This invention relates to nuclear reactors generally, and, in particular, concerns multi-cable connecting devices to be used with nuclear reactors for coupling and uncoupling a large number of reactor head cables.
Nuclear reactors have a multitude of electrical lines connected to the reactor head structure to supply power to control rod drive mechanisms, displacer rod drive mechanisms, rod position indicators and other instruments.
When the reactor head is to be disconnected or removed for maintenance or refueling, the many electrical cables associated with a reactor head must be disconnected and moved aside so that the reactor head may be opened. With advanced pressurized water reactors, for example, the various power and instrumentation cables may number from 300 to 500 for an individual reactor. If the reactor is to be opened, each one of these cables must be disconnected and later reconnected by maintenance personnel. It is imperative during these operations that the duration of the workers' exposure to radiation, which may be relatively high at the periphery of the reactor head, be as short as possible. There is the significant possibility that while the cables are hastily being reconnected they can become damaged, resulting in longer down time, additional maintenance costs, and greater worker exposure. Reactor down time is doubly costly because while the reactor is not operating replacement power must be purchased.
As the coupling and uncoupling of the hundreds of electrical connections is performed quickly, it is possible for a worker to mistakenly attempt to connect the wrong cable to a particular receptacle. Although each connection is keyed, there are a great number of cables and an incorrect connection is not impossible; at the very least, the cable plug or the receptacle may be damaged.
Reactors and their associated equipment have in some cases been designed for the purpose of reducing reactor down time during refueling. For example, a rapid refueling concept is disclosed in U.S. Pat. Nos. 3,836,429 and 3,836,430, issued to Frisch and Andrews on Sept. 17, 1974. According to these prior art concepts, the electrical cables were mounted on a movable support structure, or bridge, and were provided with sufficient cable lengths to be moved aside with the reactor head structure, allowing access to the reactor internals. The use of long cables that remain connected was necessary with the rapid refueling concept because certain systems associated with the reactor head, e.g., mechanisms for retaining the control rods, were kept active during the refueling process. However, the lengthy cables and movable supports associated with the rapid refueling system are cumbersome and require a particular design for the reactor head and its associated equipment. They also require a particular design for the containment area and cannot be retrofit into existing plants.